This invention relates to a semiconductor module with a plurality of semiconductor devices, especially a memory module with a plurality of memory chips such as a dynamic random access memory.
Each memory chip of a memory module refers a reference potential for deciding a logical value. Erroneous decisions of the memory chips are lead by a plurality of noises.
The reference potential of one of the memory chips is affected by first to third noises. The first noise is transmitted from other devices outside of the memory module. The second noise is generated by the memory chip itself. The third noise is generated by another one of the memory chip of the same memory module and transmits between the memory chips.
The first noise is depressed by a memory module comprising a low pass filter (LPF) between a system board. The memory module having the LPF is disclosed in U.S. Pat. No. 6,646,945.
The second noise is depressed by a memory module comprising a common reference electrode and a decoupling capacitor. The common reference electrode is extending in a plane parallel to a ground layer and supplies a reference potential to a plurality of memory chips directly. The decoupling capacitor is connected between the reference electrode and the ground layer.